Methods for reporting channel quality information (channel quality indicator: CQI) from a user device to a base station are being discussed by the 3rd Generation Partnership Project (3GPP), a standardization group. For example, this subject was discussed in 3GPP TSG RAN WG1 Meeting #51 (R1-075069, Nov. 5-9, 2007).
Channel quality indicators are reported regularly (regular reporting) and irregularly (irregular reporting). In regular reporting, the user device reports CQIs at regular intervals using a physical uplink control channel (PUCCH) or a physical uplink shared channel (PUSCH). In irregular reporting; the user device reports CQIs using the PUSCH in response to a request from the base station.
Meanwhile, there are several types of CQIs with respect to frequency bands: a wideband CQI indicating channel quality of the entire system frequency band and subband CQIs (frequency selective CQIs) indicating channel quality of the corresponding subbands in the system frequency band. The user device may report (A) only a wideband CQI, (B) a wideband CQI and subband CQIs selected by the user device, or (C) a wideband CQI and subband CQIs specified (or selected) by the base station.